[Federal Register Volume 77, Number 131 (Monday, July 9, 2012)]
[Rules and Regulations]
[Pages 40255-40258]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-16720]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. FAA-2012-0499; Special Conditions No. 25-466-SC]


Special Conditions: Boeing, Model 737-800; Large Non-Structural 
Glass in the Passenger Compartment

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Boeing Model 737-
800 airplane. This airplane as modified by Lufthansa Technik will have 
a novel or unusual design feature associated with the installation of 
large non-structural glass items in the cabin area of an executive 
interior occupied by passengers and crew. The installation of these 
items in a passenger compartment, which can be occupied during taxi, 
takeoff, and landing, is a novel or unusual design feature with respect 
to the material used. The applicable airworthiness regulations do not 
contain adequate or appropriate safety standards for this design 
feature. These special conditions contain the additional safety 
standards that the Administrator considers necessary to establish a 
level of safety equivalent to that established by the existing 
airworthiness standards.

DATES: Effective Date: June 25, 2012.

FOR FURTHER INFORMATION CONTACT: John Shelden, FAA, Cabin Safety 
Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98057-3356; telephone 
425-227-2785; facsimile 425-227-1232.

SUPPLEMENTARY INFORMATION:

Background

    On December 16, 2010, Lufthansa Technik AG, Weg Beim Jaeger 193, 
22335 Hamburg Germany applied for a supplemental type certificate for 
the installation of large non-structural glass items in the cabin area 
of the executive interior occupied by passengers and crew in a Boeing 
Model 737-800. The Boeing Model 737-800, approved under Type 
Certificate No. A16WE, is a large transport category airplane that is

[[Page 40256]]

limited to 189 passengers or less, depending on the interior 
configuration. This specific Boeing Model 737-800 configuration 
includes seating provisions for 34 passengers.

Type Certification Basis

    Under the provisions of Title 14, Code of the Federal Regulations 
(14 CFR) 21.101, Lufthansa Technik must show that the Boeing Model 737-
800, as changed, continues to meet the applicable provisions of the 
regulations incorporated by reference in Type Certificate No. A16WE or 
the applicable regulations in effect on the date of application for the 
change. The regulations incorporated by reference in the type 
certificate are commonly referred to as the ``original type 
certification basis.'' The regulations incorporated by reference in 
Type Certificate No. A16WE are as follows: 14 CFR part 25 as amended by 
Amendments 25-1 through 25-77 with exceptions for the Boeing Model 737-
800. In addition, the certification basis includes certain special 
conditions, exemptions, or later amended sections of the applicable 
part that are not relevant to these special conditions.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Boeing Model 737-800 because of a 
novel or unusual design feature, special conditions are prescribed 
under the provisions of Sec.  21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the applicant apply for a supplemental type 
certificate to modify any other model included on the same type 
certificate to incorporate the same or similar novel or unusual design 
feature, the special conditions would also apply to the other model 
under Sec.  21.101.
    In addition to the applicable airworthiness regulations and special 
conditions, the Boeing Model 737-800 must comply with the fuel vent and 
exhaust emission requirements of 14 CFR part 34 and the noise 
certification requirements of 14 CFR part 36.
    The FAA issues special conditions, as defined in 14 CFR 11.19, in 
accordance with Sec.  11.38, and they become part of the type-
certification basis under Sec.  21.101.

Novel or Unusual Design Features

    The Boeing Model 737-800 will incorporate the following novel or 
unusual design features: The installation of large non-structural glass 
items, typically in the form of glass sheets in the cabin area of an 
executive interior occupied by passengers and crew.
    These installations would be for aesthetic purposes, not for 
safety, in components other than windshields or windows. For these 
special conditions, a large glass item is 4 kg (approximately 10 
pounds) and greater in mass. This limit was established as the mass at 
which a glass component could be expected to potentially cause 
widespread injury if it were to shatter or break free from its 
retention system.
    These special conditions address the novel and unusual design 
features for the use of large non-structural glass in the passenger 
cabin. These large glass items would be installed in occupied rooms or 
areas during taxi, take off, and landing, or rooms or areas that 
occupants do have to enter or pass through to get to any emergency 
exit. The installations of large non-structural glass items may 
include, but are not limited to, the following items:
     Glass partitions.
     Glass attached to the ceiling.
     Wall/door mounted mirrors/glass panels.

Discussion

    The existing part 25 regulations only address the use of glass in 
windshields, instrument or display transparencies, or window 
applications. The regulations treat glass as unique for special 
applications where no other material will serve and address the adverse 
properties of glass.
    Section 25.775, ``Window and windshields,'' provides for the use of 
glass in airplanes but limits glass to windshields and windows. 
Furthermore, except for bolted-in windshields, there is limited 
experience with either adhesive or mechanical retention methods for 
large glass objects installed in an airplane subject to high loads 
supported by flexible restraints.
    The FAA has accepted the following uses of glass in the passenger 
cabin under the current regulations:
    1. Glass items installed in rooms or areas in the cabin that are 
not occupied during taxi, take off, and landing, and occupants do not 
have to enter or pass through the room or area to get to any emergency 
exit.
    2. Glass items integrated into a functional device whose operation 
is dependent upon the characteristics of glass, such as instrument or 
indicator protective transparencies, or monitor screens such as liquid 
crystal display (LCD) or plasma displays. These glass items may be 
installed in any area in the cabin regardless of occupancy during taxi, 
take-off, and landing. Acceptable means for these items may depend on 
the size and specific location of the device.
    3. Small glass items installed in occupied rooms or areas during 
taxi, take off, and landing, or rooms or areas that occupants do have 
to enter or pass through to get to any emergency exit. For the purposes 
of these special conditions, a small glass item is less than 4 kg in 
mass or a group of glass items weighing less than 4 kg in mass.
    The glass items in numbers one, two, and three (above) have been 
restricted to applications where the potential for injury is either 
highly localized (such as instrument faces) or the location is such 
that injury due to failure of the glass is unlikely (e.g., mirrors in 
lavatories). These glass items are subject to the inertia loads 
contained in Sec.  25.561 and maximum positive differential pressure 
for items like monitors, but are not subject to these special 
conditions. They have been found acceptable through project specific 
means of compliance requiring testing to meet the requirement in Sec.  
25.785(d) and by adding a protective polycarbonate layer that covers 
the glass exposed to the cabin.
    The use of glass in airplanes utilizes the one unique 
characteristic of glass--its capability for undistorted or controlled 
light transmittance, or transparency. Glass, in its basic form as 
annealed, untreated sheet, plate, or float glass, when compared to 
metals, is extremely notch-sensitive, has a low fracture resistance, 
has a low modulus of elasticity, and can be highly variable in its 
properties. While reasonably strong, it is not a desirable material for 
traditional aircraft applications because, as a solo component, it is 
heavy (about the same density as aluminum). In addition, when glass 
fails, it can break into extremely sharp fragments that have the 
potential for injury above and beyond simple impact and have been known 
to be lethal.
    The proposed special conditions address installing glass in much 
larger sizes than previously accepted and in a multitude of locations 
and applications, instead of using more traditional aircraft materials. 
In most, if not all cases, the glass will not be covered with a 
polycarbonate layer. Additionally, the retention of glass of this size 
and weight is not amenable to conventional techniques currently 
utilized in airplane cabins.
    The proposed special conditions consider the unusual material 
properties of glass as an interior material that have limited or 
prevented its use in the past, and address the performance standards 
needed to ensure that those properties do not reduce the level of 
safety

[[Page 40257]]

intended by the regulations. They address the use of large glass items 
installed in occupied rooms or areas during taxi, take off, and 
landing, or rooms or areas that occupants do have to enter or pass 
through to get to any emergency exit.
    The special conditions define a large glass component threshold of 
4 kg, which is based on an assessment of the mass dislodged during a 
high ``g'' level (as defined in Sec.  25.562) event. Groupings of glass 
components that total more than 4 kg would also need to be included. 
The applicable performance standards in the regulations for the 
installation of these components also apply and should not adversely 
affect the standards provided below. For example, heat release and 
smoke density testing should not result in fragmentation of the 
component.
    For large glass components mounted in a cabin occupied by 
passengers or crew that are not otherwise protected from the injurious 
effects of failure of the glass component, the following apply:
    Material. The glass used must be tempered or otherwise treated to 
ensure that when fractured, it breaks into small pieces with relatively 
dull edges. This must be demonstrated by testing to failure. Tests 
similar to ANSI/SAE Z26.1 section 5.7, Test 7 would be acceptable.
    Fragmentation. The glass component construction must control the 
fragmentation of the glass to minimize the danger from flying glass 
shards or pieces. Impact and puncture testing to failure must 
demonstrate this. Tests similar to ANSI/SAE Z26.1 section 5.9, Test 9 
adjusted to ensure cracking the glass would be acceptable.
    Strength. The glass component, as installed in the airplane, must 
be strong enough to meet the load requirements for all flight and 
landing loads and all of the emergency landing conditions in subparts C 
and D of part 25. In addition, glass components that are located such 
that they are not protected from contact with cabin occupants must be 
designed for abusive loading without failure, such as impact from 
service carts, or occupants stumbling into, leaning against, sitting 
on, or performing other intentional or unintentional forceful contact. 
This must be demonstrated by static structural testing to ultimate load 
except that the critical loading condition must be tested to failure. 
The tested glass component must have all features that affect component 
strength, such as etched surfaces, cut or engraved designs, holes, and 
so forth.
    Retention. The glass component, as installed in the airplane, must 
not come free of its restraint or mounting system in the event of an 
emergency landing. Based on the characteristics of a large glass 
component, dynamic tests should be performed to demonstrate that the 
occupants would be protected up to the load levels required by the 
certification basis of the airplane. A single test for the most 
critical loading for the installed component would be sufficient. This 
may be accomplished by using already accepted methods for dynamic 
testing.
    Analysis may be used in lieu of testing if the applicant has 
validated the strength models and dynamic simulation models used 
against static tests to failure and dynamic testing to the above 
requirements and can predict structural failure and dynamic response 
and inertial load. The glass material properties must meet Sec.  
25.613, ``Material strength properties and material design values.'' 
The effect of design details, such as geometric discontinuities or 
surface finish, must be accounted for in the test/analysis.

Discussion of Comments

    Notice of proposed special conditions No. 25-12-01-SC for the 
Boeing Model 737-800 airplane was published in the Federal Register on 
May 15, 2012 (77 FR 28533). No comments were received, and the special 
conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Boeing Model 737-800. Should Lufthansa Technik apply at a later date 
for a supplemental type certificate to modify any other model included 
on Type Certificate No. A16WE to incorporate the same novel or unusual 
design feature, the special conditions would apply to that model as 
well.
    Under standard practice, the effective date of final special 
conditions would be 30 days after the date of publication in the 
Federal Register; however, as the date for the approval of the 
supplemental type certificate for the Boeing Model 737-800 is imminent, 
the FAA finds that good cause exists to make these special conditions 
effective upon issuance.

Conclusion

    This action affects only certain novel or unusual design features 
on one model of airplane. It is not a rule of general applicability, 
and it affects only the applicant who applied to the FAA for approval 
of these features on the airplane.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for Boeing Model 737-800 airplanes 
modified by Lufthansa Technik AG. For these special conditions, a large 
glass component is 4 kg (approximately 10 pounds) and greater in mass, 
or a grouping of glass components that total more than 4 kg.
    1. Boeing Model 737-800 Airplane; Large Non-Structural Glass in the 
Passenger Compartment.
    The airplane must not be operated for hire or offered for common 
carriage. This provision does not preclude the operator from receiving 
remuneration to the extent consistent with 14 CFR parts 125 and 91, 
subpart F, as applicable.
    2. Material Fragmentation. The glass used to fabricate the 
component must be tempered or treated to ensure that, when fractured, 
it breaks into small pieces with relatively dull edges. In addition, it 
must be shown that fragmentation of the glass is controlled to reduce 
the danger from flying glass shards or pieces. This must be 
demonstrated by testing to failure.
    3. Component Strength. The glass component must be strong enough to 
meet the load requirements for all flight and landing loads including 
any of the applicable emergency landing conditions in subparts C and D 
of part 25. Abuse loading without failure, such as impact from 
occupants stumbling into, leaning against, sitting on, or performing 
other intentional or unintentional forceful contact, must also be 
demonstrated. This must be demonstrated by static structural testing to 
ultimate load, except that the critical loading condition must be 
tested to failure in the as-installed condition. The tested glass must 
have all features that affect component strength, such as etched 
surfaces, cut or engraved designs, holes, and so forth. Glass pieces 
must be non-hazardous.
    4. Component Retention. The glass component, as installed in the 
airplane, must not come free of its restraint or mounting system in the 
event of an emergency landing. A test must be performed to demonstrate 
that the occupants would be protected from the effects of the component 
failing or

[[Page 40258]]

becoming free of restraint under dynamic loading. The dynamic loading 
of Sec.  25.562(b)(2) is considered an acceptable dynamic event. The 
applicant may propose an alternate pulse; however, the impulse and peak 
load may not be less than that of Sec.  25.562(b)(2). As an alternative 
to a dynamic test, static testing may be used if the loading is 
assessed as equivalent as or more critical than a dynamic test, based 
upon validated dynamic analysis. Both the primary directional loading 
and rebound conditions need to be assessed.
    5. Instructions for Continued Airworthiness. The instructions for 
continued airworthiness must reflect the fastening method used and must 
ensure the reliability of the methods used (e.g., life limit of 
adhesives, or clamp connection). Inspection methods and intervals must 
be defined based upon adhesion data from the manufacturer of the 
adhesive or actual adhesion test data, if necessary.

    Issued in Renton, Washington, on June 25, 2012.
K.C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 2012-16720 Filed 7-6-12; 8:45 am]
BILLING CODE 4910-13-P